The invention relates to stack modules for supporting and containing a plurality of flat packaged electrical devices, in particular semiconductor devices such as thyristors or rectifiers, which are to be maintained under pressure for good thermal and electrical conduction.
Typical stack modules of the prior art are described in U.S. Pat. No. 3,523,215 of J. J. Steinmetz et al. and No. 3,447,118 of H. E. Ferree. The stack module of the aforementioned patents include upper and lower members connected by vertical tension members for holding a stack of thyristors each sandwiched between two heat sinks. An adjustable force is applied to the top of the stack through the center of the upper member through adjustable force means including bolt, nut and spring structures.
In the stack module of the prior art, the alternate heat sinks are used as connecting elements for the electrical power, and also as thermal conductors. They are generally made of solid copper, and are very heavy. Each semiconductor device usually lay on the upper surface of the adjacent lower heat sink in good mechanical, thermal and electrical contact, and so does the adjacent upper heat sink when mounted on top of the sandwiched semiconductor device. This makes a heavy stack of parts of which the heat sinks are held by connectors to the busses and feeders of the bridge of semiconductor devices. It appears that a problem with the stack modules of the prior art occurs when a semiconductor devices has to be tested, taken away, and/or replaced. Up to now for maintenance the entire stack module had to be dismantled so that one can recognize and reach a defective semiconductor device.